Cigarettes are generally manufactured by wrapping tobacco shreds with wrapping paper to form a tobacco rod and cutting the tobacco rod to a predetermined length. The wrapping paper is an elongated one—about 27 mm in width, and is provided in the rolled-up form, i.e., in the form of a roll.
Incidentally, a smoker sometimes drops a cigarette on a floor, a carpet or the like while smoking. In such cases, the cigarette should preferably stop burning naturally. To this end, attempts have been made to form wrapping paper with low flame spread portions. For instance, wrapping paper is increased in thickness by, for example, affixing pieces of paper containing a low flame spread material to one side of wrapping paper in approximately equally spaced stripes, or a diluted solution of a low flame spread material is coated on (applied to) wrapping paper in approximately equally spaced stripes, or other processing is done. Another attempt to inspect the quality of low flame spread portions of wrapping paper has also been made.
For example, a wrapping paper inspection apparatus described in Japanese national patent publication (Tokuhyo) no. 2001-509366 is designed to inspect wrapping paper consisting of base cigarette paper to which pulp layers of cellulose (microcrystalline cellulose, amylopectin or the like), which is a low flame spread material, are affixed in approximately equally spaced stripes. Specifically, this inspection apparatus is designed to irradiate light from a light source such as an infrared emitting diode to the wrapping paper while unwinding it from a roll, detect variation in the amount of light reflected from the wrapping paper by an optical sensor, and optically determine the quality of affixation of the pulp layers of low flame spread material to the wrapping paper.
In other words, this wrapping paper inspection apparatus uses a difference in light reflectance between the base cigarette paper of the wrapping paper and the low flame spread material affixed thereto, and is designed that spot light is irradiated onto one side of the wrapping paper to which the low flame spread material is affixed, and light that is reflected therefrom and transmitted through a detector lens, a filter, and a polarizer, is detected by a detector.
As mentioned above, there is wrapping paper having a low flame spread property imparted by increasing the thickness by affixing a material to base cigarette paper, the material having the same property as the base cigarette paper. In this type of wrapping paper where the base cigarette paper and the low flame spread portion are the same in material and there is no difference in light reflectance therebetween, it is impossible to detect defects in the low flame spread portion by using a difference in light reflectance between the base cigarette paper and the low flame spread material.
Wrapping paper applied with sodium alginate, which is a low flame spread material, also has a problem that it is difficult to reliably detect defects in the coating of the low flame spread material, since there is no noticeable difference in light reflectance between base cigarette paper and regions coated with sodium alginate.